Aerosol characterization in an oceanic context around Reunion Island (AEROMARINE field campaign)

Faustine Mascaut (1) , Olivier Pujol (1) , Bert Verreyken (2, 3, 4) , Raphaël Peroni (1) , Jean Marc Metzger (5) , Luc Blarel (1) , Thierry Podvin (1) , Philippe Goloub (1) , Karine Sellegri (6) , Troy Thornberry (7, 8) , Valentin Duflot (2) , Pierre Tulet (9) , Jérôme Brioude (2)

1 LOA - Laboratoire d’Optique Atmosphérique - UMR 8518
2 LACy - Laboratoire de l'Atmosphère et des Cyclones
3 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
4 UGENT - Universiteit Gent = Ghent University
5 OSU-Réunion - Observatoire des Sciences de l'Univers de La Réunion
6 LaMP - Laboratoire de Météorologie Physique
7 CSL - NOAA Chemical Sciences Laboratory
8 University of Colorado [Boulder]
9 LAERO - Laboratoire d'aérologie

This article presents the results of the AEROMARINE field campaign which took place between February and April 2019 off the coast of Reunion Island in the South West Indian Ocean basin. The Southern Indian Ocean is of major interest for the study of marine aerosols, their distribution and variability. Six instrumented light plane flights and a ground-based microwave radiometer were used during the field campaign. These measurements were compared with the long-term measurements of the AERONET sun-photometer (based in St Denis, Reunion Island) and various instruments of the high altitude Maïdo Observatory (2.2 km above sea level, Reunion Island). These results were also analyzed using different model outputs: (i) the AROME mesoscale weather forecast model to work on the thermodynamics of the boundary layer, (ii) the FLEXPART-AROME Lagrangian particle dispersion model to assess the geographical and vertical origin of air masses, and (iii) the chemical transport model CAMS (Copernicus Atmosphere Monitoring Service) to work on the aerosol chemical composition of air masses. This allowed to highlight two points: (1) the atmospheric layer above 1.5 km is mainly composed of aerosols from the regional background; (2) the local environment (ocean or island) has little impact on the measured concentrations. Marine aerosols emitted locally are mostly measured below 0.5 km. The daytime marine aerosol distributions in the free troposphere measured by the aircraft were compared to the night-time aerosol distributions measured at the high altitude Maïdo Observatory when the Observatory is located in the free troposphere. The results indicate that this high altitude site of measurements is representative of the marine aerosol concentrations in the free troposphere. We also found that the CAMS reanalyses overestimated the aerosol optical depth in this region. Finally, our study strongly suggests that the AERONET station in St Denis (Reunion Island) can be considered as a representative marine station under the Tropics.

Mots clés: Sea salt aerosols, Pristine conditions, Southern indian Ocean, AEROMARINE field Campaign

Domaines: Physique [physics]; Sciences de l'environnement

Faustine Mascaut, Olivier Pujol, Bert Verreyken, Raphaël Peroni, Jean Marc Metzger, et al.. Aerosol characterization in an oceanic context around Reunion Island (AEROMARINE field campaign). Atmospheric Environment, 2022, 268, pp.118770. ⟨10.1016/j.atmosenv.2021.118770⟩. ⟨hal-03815612⟩